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1987 Shelby GLHS #0958
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It should be a drop in. It would keep the carbon ring from locking up as soon. Anything to help lessen VNT maintenance!
 

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A little bit of info: A good friend of mine(v8sr4u) examined the calibrations to compare the CSX VNT and production SBECs. Besides slightly different spark and boost curves, the CSX version completely lacks the vane cleaning cycle that the Lebaron, Daytona, and Shadow CS had that would run the vanes every time the vehicle is started.
I'd imagine that came from learning from CSX-VNT production & service records the year before the '90 Dodge Daytona VNT.
Does cleaning the vanes have anything to do with oil leakage from the turbo?
I remember Tim Pettijohn saying something about the CSX-VNT leaking oil into the PCV filter in the airbox.
 

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1987 Shelby GLHS #0958
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Fueling mapping was not as advanced then as it is now. The exhaust system was a very cruddy place. Any nook and cranny is just begging to get filled with carbon. Having complicated moving parts in there blows my mind. We use carbon swarf slurry to generate a permanent press fit between two metal parts where I work sometimes. Seizes them right up! It's a miracle the vanes worked for more than two months.
 

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I’ll jump in and follow this one as well, wished I would have found it before I bought all new 2 1/2” exhaust and installed it. No turning back now. I did also get a new stage 2 cal from FWD Performance that I’m looking forward to putting in. These are the only engine mods I’ll do. Just wanted to have a fun car to play with. Sounds like the over boost issue is almost un-resolvable?
 

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I’ll jump in and follow this one as well, wished I would have found it before I bought all new 2 1/2” exhaust and installed it. No turning back now. I did also get a new stage 2 cal from FWD Performance that I’m looking forward to putting in. These are the only engine mods I’ll do. Just wanted to have a fun car to play with. Sounds like the over boost issue is almost un-resolvable?
"Sounds like the overboost issue is almost unsolvable?"
Without the proper exhaust system backpressure your statement is correct, you will always have an overboost issue, the exhaust system on a VNT equipped vehicle was/is designed to be part of the boost control system.
 

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The few guys I knew with VNT's replaced the VNT Turbo with a T-II or MP Super 60.

No more free flowing exhaust issues but I believe they ran manual boost control.

They kept the VNT electronics and had no reliability or performance issues.

When I had free flowing overboost issues with my Mitsu I found a solution.

I placed a minor restriction at my exhaust tip.

Virtually invisible and it worked fine.

Thanks
Randy



I’ll jump in and follow this one as well, wished I would have found it before I bought all new 2 1/2” exhaust and installed it. No turning back now. I did also get a new stage 2 cal from FWD Performance that I’m looking forward to putting in. These are the only engine mods I’ll do. Just wanted to have a fun car to play with. Sounds like the over boost issue is almost un-resolvable?
 

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1987 Shelby GLHS #0958
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Randy, my GTC VNT coupe was set up that way with an MBC. I just now gave a good VNT turbo to my friend that ended up with the car. He's going to try to put it back to being stock. He already painted it. It is SLICK looking.
 

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I just looked back here and thought about the solenoid test cycle available on the Snap-on scanner. Is that test able to be done with the engine idling? If so, a person may be able to run their own cleaning cycle on a regular basis to try to slow down the carbon build up that bricks the VNT.
 

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Also. Overboosting on the VNT is inherently part of the design since the nozzle simply controls how fast the turbine spins but cannot bypass exhaust gasses around the turbine. Creating more flow after the turbine will of course cause the turbine to spool out of control. There is absolutely no reason you can't install an external type wastegate anywhere in the exhaust manifold. Especially in the "N" manifold(ultra high nickel alloy) which is extremely resistant to cracks.(used on the production VNT cars, though I do not know if it was used on the Shelby cars) This external wastegate could be controlled by a manual boost controller to limit max boost. From what I have read over the years, the VNT wastegate stuff hasn't even been attempted. ND performance used to have 3 bar tunes for VNT, but I never saw anything for boost control for modified exhaust. If anyone has read about someone installing a wastegate before the VNT turbo, please let me know. I would love to read about it!

Talking about this stuff makes me mad. I had to give away my GTC VNT coupe when the city got on me about having too many cars. I wanted to test my "theories" and record results using that car. Hopefully my friend that owns it now will be up for it. I just gave him the final piece of the puzzle a week ago. The VNT only turbo oil drain pipe.
 
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